It has been a well-known practice in cardiology to record electrocardiograph data over a protracted period, usually twenty-four hours, on a battery-powered magnetic tape recorder carried by the patient, and then play back this recording at many times (usually 60.times. or more) the recording speed for analysis. The taped record may include recorded time or other indicia to correlate aberrations in the heartbeat with significant stressful or other events during the recording session. The analysis of the recorded electrocardiograph record may be achieved by a computer program or by observation by a skilled technician, either of which marks portions of the record for printout and detailed study by a cardiologist.
In such a protocol it is desirable that the portable recording unit be as small and light as possible. Thus, it is common practice to employ magnetic tape cassettes such as those used in audio recorders. A C-120 cassette is one such type of cassette.
Since a twenty-four hour recording requires a very slow tape speed and since the ECG signals must be recorded with very high fidelity, it is a necessity that very high quality tape be used and that a previously unused (virgin) tape be used. To enhance the fidelity and compensate for the slow tape speed, analog to digital conversion and multi-channel recording may be utilized.
Another necessity, in addition to the use of a virgin tape, is the assurance of the use of a fresh battery for each use. To issue instructions to the patient or the installing technician may not in all cases assure a virgin tape and a fresh battery. While a weak battery or used tape is not injurious to the patient, the test procedure is vexatious, and it is certainly desirable to minimize the chances of producing an inferior and possibly unusable record.
It is known in the art of photography to package a film pack and battery in an integrated package in self-developing "instant" camera. This one-time use assures a fresh battery for each film pack. However, once exposed the film cannot be re-used, so there is no concern over the re-use of the film.